Zoxamide accumulation and retention evaluation after nanosuspension technology application in tomato plant

BACKGROUND: Low water solubility of pesticide requires formulations with high levels of stabilizers and organic solvents. Moreover, only 0.1% of the applied pesticides formulation reaches the target, while 99.9% spreads in the surrounding environment. Therefore, there is the need for more efficient and environmentally sustainable alternatives. RESULTS: Zoxamide (ZO) nanosuspension was prepared through a media milling technique by using the stabilizer polysorbate 80. The thin and acicular crystals obtained, showed particle size of 227 nm, polydispersion index of 0.247 and zeta potential of −28 mV. Dimensional data and morphology of ZO nanocrystals alone, on tomato leaves and berries, were confirmed by scanning electron microscopy. The reduction in size for ZO crystals obtained after the milling process increased pesticide water solubility till 39.6 mg L−1, about 1.6 the solubility obtained with a conventional commercial formulation. Field and dip contamination trials performed on tomato plants showed the nanosuspension's ability to increase ZO deposition and accumulation versus a coarse ZO suspension and commercial formulation, respectively. CONCLUSIONS: The nanoformulation proposed, resulted in low cost and was easy to make. Moreover, the organic solvent-free composition together with a low surfactant addition assured a minor environmental impact. Finally, the increased retention and deposition of the fungicide can reduce the amounts of ZO formulation applied to tomatoes

Heterogeneous atmospheric degradation of pesticides by ozone: Influence of relative humidity and particle type

International audienceIn the atmosphere pesticides can be adsorbed on the surface of particles, depending on their physico-chemical properties. They can react with atmospheric oxidants such as ozone but parameters influencing the degradation kinetics are not clear enough. In this study the heterogeneous ozonolysis of eight commonly used pesticides (i.e., difenoconazole, tetraconazole, cyprodinil, fipronil, oxadiazon, pendimethalin, deltamethrin, and permethrin) adsorbed on hydrophobic and hydrophilic silicas, and Arizona dust at relative humidity ranging from 0% to 80% was investigated. Under experimental conditions, only cyprodinil, deltamethrin, permethrin and pendimethalin were degraded by ozone. Second-order kinetic constants calculated for the pesticides degraded by ozone ranged from (4.7 ± 0.4) × 10−20 cm3 molecule−1 s−1 (pendimethalin, hydrophobic silica, 55% RH) to (2.3 ± 0.4) × 10−17 cm3 molecule−1 s−1 (cyprodinil, Arizona dust, 0% RH). Results obtained can contribute to a better understanding of the atmospheric fate of pesticides in the particulate phase and show the importance of taking humidity and particle type into account for the determination of pesticides atmospheric half-lives